1. Field of the Invention
The present invention relates to an inkjet printing apparatus and an inkjet printing method.
2. Description of the Related Art
Ink used in an inkjet printing apparatus is a liquid, so that, if nozzles of a print head are exposed to open air, ink in the nozzles may become viscous or stick to the interior of the nozzles. This in turn may cause an improper ejection in which landing positions of ink droplets deviate from intended ones, or an ejection failure in which ink droplets fail to be squirted at all, degrading a quality of printed images.
To deal with this problem, the inkjet printing apparatus has a recovery mechanism or device to eliminate the improper ejection and restore the normal ink ejection performance. This recovery device performs a suction-based recovery operation and a preliminary ejection. The suction-based recovery operation involves generating a negative pressure within a print head by suction or pressurization to suck out ink from the print head. The preliminary ejection causes the print head to eject ink without regard to the printing operation. These recovery operations are performed after the nozzles have been exposed to open air for a predetermined period of time, in order to discharge from the nozzles viscous ink and nozzle-sticking ink.
The preliminary ejection is normally performed at a cap, that is located near the home position and used for a suction-based recovery operation, and also at a preliminary ejection port (located, for example, across the print area from the home position). However, since the preliminary ejection is done separately from the normal printing operation, it takes time in addition to the time spent for printing. This means that as the number of preliminary ejections increases, throughput will inevitably deteriorate. That is, the number of preliminary ejections greatly influences the throughput.
Under these circumstances, Japanese Patent Laid-Open No. 2005-349604 discloses a method that involves acquiring information on a print medium size and a print medium feed position in the direction of scan (i.e., whether it is on the reference side or not) and, based on the information thus acquired, setting from the cap and the preliminary ejection port a combination of positions where the preliminary ejection is to be performed.
For example, a check is made as to whether the size (width) in the scan direction of the print medium is less than half a maximum scan width of the carriage. If the print medium size is found to be greater than half the maximum scan width, a setting is made to execute the preliminary ejection both at the cap, which is located on the reference side (home position side), and at the preliminary ejection port on the opposite side. If the width of the print medium is less than half the maximum scan width and the print medium feed position is on the reference side, the preliminary ejection is set to be executed only at the cap.
This enables the preliminary ejection execution position to be controlled appropriately without lowering throughput.
With the control method disclosed in Japanese Patent Laid-Open No. 2005-349604, however, the position where the preliminary ejection is performed is determined only from the information on the size and position of the print medium. So, when the print medium is large in size, even if a small-size image is to be printed in an area near the reference side, the preliminary ejection is performed both at the cap on the reference side and at the preliminary ejection port on the non-reference side.